[C++-sig] Injecting void* and HWND handling code from Py++

[Niall Douglas]

On 27 May 2012 at 20:37, Suresh Joshi wrote:

> (2) From Python, I would like to manipulate the memory of a buffer stored
> within Foo. In my REAL code, the only accessor I can use is Address() which
> returns a void pointer, which Py++/BP flips into an opaque pointer (which I
> don't think I can use to manipulate m_buffer's memory in Python). 
> 
> One option is ctypes, but I frankly just don't know how to combine that with
> BP for the purpose of manipulating data behind a void*, even after having
> looked at the ctypes integration code in the Py++ docs.
> 
> The other option is to do something like what I did with the fake VoidPtr()
> accessor. I could create accessors like VoidPtrAsUChar() for example, and
> then expose those using the return_addressof call policy (hopefully!). If
> this is, in fact, a valid approach, then I have the same question as
> above... 
> 
> Given that I can't change the Foo.hpp code, is there a clean way of
> injecting those AsUChar, AsInt, As... helper methods straight into the
> wrapper code, so that they call Address() internally and then
> reinterpret_cast the returned void* into something more useful and
> accessible in Python?

If you really, really want to do this, I would have the wrapper of 
your Address method return an array-like interface e.g. like a 
std::vector<>. Look into the indexing suite - a method of 
implementing direct image bitmap access from python came up on this 
list a few years back.

Niall

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